Add propOr

[Frikki]

Add propOr

[TylorS]

What do you think about parameter order?

propOr<O extends object, K extends keyof O>(key: K, defaultValue: O[K], obj: O): O[K] 
// or
 propOr<O extends object, K extends keyof O>(defaultValue: O[K], key: K, obj: O): O[K] 

I think I favor the latter because the defaultValue should probably dictate which key you need from the objects you have and will generally be better for composition.

[Frikki]

Yes, latter.